Radar systems provide air traffic control personnel with accurate navigational information to allow them to guide aircraft on approach to a safe landing, during both clear and instrument flight rule weather conditions. Radar systems are composed of the radar and associated communications and electronics equipment and external antenna systems. Radar systems detect and track aircraft approaching a runway for landing and may be deployed as mobile radar systems.
The external antenna system of a radar system requires careful and precise positioning for the radar to perform its function. During installation all antennas require a bore site adjustment of the antenna reflectors so they reflect at a predetermined elevation and distance from the antenna. This bore site adjustment is achieved with reference reflectors that are positioned once an antenna site survey has been completed. The positioning of the reference reflector and adjustment of the antenna reflector may require angle offset calculations. These offset calculations are required using conventional techniques because the surveyor can only position his tripod on the ground near the antenna. In most cases, the surveying equipment will be positioned at a lower elevation than the antenna target points.
Surveying may be done with the help of a theodolite. A theodolite is an instrument for measuring both horizontal and vertical angles, as used in triangulation networks. A modern theodolite consists of a telescope mounted movably within two perpendicular axes, the horizontal or trunnion axis, and the vertical axis. When the telescope is pointed at a desired object, the angle of each of these axes can be measured with great precision, typically on the scale of arc seconds. A transit is a specialized type of theodolite that is able to “flop over” (“transit the scope”) to allow easy back-siting and double of angles for error reduction.
Using the theodolite, a survey team may direct a reference reflector crew in positioning a reference reflector at the proper elevation required for bore siting the antenna.
Using conventional techniques, it is often necessary for installation and calibration teams to double check the position of the reference reflector due to incorrect survey calculations. Incorrect survey calculations may be caused by the angle offset calculations that must be performed if the theodolite is positioned at a lower elevation than the antenna target points.